The prevalence of nosocomial (hospital-acquired) infection adversely affects the quality and cost of healthcare globally. Primary bloodstream infections, which are typically precipitated by intravenous infusions, account for 8% of all nosocomial infections. A heightened awareness of transmission of potentially pathogenic bacterial organisms has lead to implementation of various preventative measures. In the United States alone, 50,000 to 120,000 patients per year develop infusion-related bacterial infections. With an average cost of treatment of such infections at $15,000 per incident, the overall cost to this country can exceed 2 billion dollars annually. By way of further background, see Tarara, D. and Wenzel, R. P., Nosocomial Bloodstream Infection in Critically Ill Patients, JAMA 1994; 271, 1598-1601; Edgeworth, J., Treacher, D. and Eykyn, S., A 25-year Study of Nosocomial Bacteremia in an Intensive Care Unit, Crit. Care Med. 1999; 27:1421-1428; and Laupland, K. B., Zygun, D. A., Davies, D., et al., Population-based Assessment of Intensive Care Unit-acquired Bloodstream Infection in Adults: Incidence, Risk Factors, and Associated Mortality Rate, Crit. Care Med., 2002; 30:2462-2467.
In the course of normal medical practice, both the intravenous (IV) fluid (commonly comprising colloid or crystalloid solutions), as well as the internal surfaces of the fluid path (commonly transparent polyvinylchloride (PVC) IV tubing) are sterile. This is to ensure that the parenteral compartment of the patient is not seeded with microbial agents.
Any manipulation or perturbation to the integrity of the closed intravenous system can create an opportunity for a breach in the sterility. One recent, well-controlled study found a mean bacterial colonization rate of fluids of approximately 16%. See, by way of background, Loftus, R W, et al., Transmission of Pathogenic Bacterial Organisms in the Anesthesia Work Area, Anesthesiology 109 (2008): 399-407.)
In immuno-compromised patients, and in fluids that may in fact support bacterial growth, the risk for significant infection is ever greater. One such manipulation of the sterile fluid system involves the very common practice of the administration of medications, either by bolus or infusion. This creates the opportunity for contamination of the system at, for example, the fluid interface (e.g. a luer fitting).
A recent study at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., USA found that the lumen of intra-operative stopcock sets and associated fluid interfaces (i.e. luer fittings, etc.), previously found at the onset of surgery to be sterile, yielded positive cultures of bacterial organisms in 32% of the cases investigated, at the conclusion of the operative procedure. Twenty-five percent of patients who had positive stopcocks developed nosocomial infections, twice that of the group that did not have stopcock contamination.
A system that can reliably render the parenteral fluids sterile, once the sterile integrity of the system has been breached, at a point downstream from the provider's last contact with the fluid path would be advantageous. It could thereby limit the exposure of risk to the patient significantly. This can effectively have the potential to save billions of health care dollars and millions of lives.
Presently, there are no available reliable commercial mechanisms for rendering parenteral fluid, or any fluid meant for infusion into patients, re-sterilized in real-time, if the sterile condition is breached, short of replacing the fluid and intravenous tubing assembly.
One possible approach to reducing the risk of re-introducing microbial organisms once the sterile barrier had been breached is to employ an inline microbial filter. A pore size of 0.22 microns is necessary for sterile filtration, but such a smaller pore size rating would typically create a greater resistance to flow, and is not tenable for the general range of IV fluid flow rates required in surgery and in treating critically ill patients. By way of example, necessary ranges for the flow of IV fluid range from 5-1000 ml/hr. Furthermore, periodic removal of such an inline filter as it becomes filled with particulates, and its efficiency diminishes, can leave open the possibility for further breaches in the sterile barrier. Because parenteral fluid line contamination is primarily caused by healthcare provider fluid interface or injection points, aka “breach points,” it is necessary to ensure there are no further breach points between the device inlet and the patient's parenteral access point (typically an IV catheter).
Other physicochemical techniques also exist that ensure the sterility of fluids includes the physical methods of heat and/or radiation. These are not necessarily viable options as there may be detrimental effects upon structural components of blood and pharmaceutical products.
Accordingly, it is desirable to provide a system for sterilizing IV fluid downstream of any breach points. The system should desirably perform sterilization efficiently at needed flow rates, can sterilize a wide range of fluids without damaging or chemically degrading them, and that generally operates free of a need for replacement or service during a typical IV treatment cycle.